1. Field of the Invention
The present invention relates to a liquid crystal display (LCD) device, and more particularly, to an LCD device which controls operations of backlights by comparing a power source for driving the backlights to a power source for driving a video processing board, the power sources being supplied separately from each other.
2. Description of Related Art
As demands for display devices increase, lower power consumption which is directly related to usable time of the device is researched actively. Especially, in case of the display device used in portable devices with screens, liquid crystal displays (LCD) are mainly used as the displays. The LCD device, which was developed for substituting a cathode ray tube (CRT), has advantages such as small size, light weight, and low power consumption, thus the LCD is also used in a large scale information display apparatus as well as in a laptop computer and a desktop computer.
Since the LCD device cannot illuminate itself, information is displayed by reflecting outer light passing through an LCD panel or by installing an additional light source, that is, a backlight assembly on a back surface of the LCD panel.
The backlight assembly includes a lamp unit for radiating the light, a light guide panel for guiding the light radiated from the lamp unit toward the LCD panel, and optical sheets for diffusing and condensing the light guided by the light guide panel to improve an efficiency of the light.
The lamp unit includes a lamp used as the light source of the LCD device, a reflecting panel for reflecting the light radiated from the lamp to improve the light efficiency, and an inverter connected to the lamp using a wire to apply a voltage to the lamp.
Recently, as LCD devices have become larger, a direct type LCD device, in which the backlight is directly installed on the LCD, has been used.
The number of backlights increases for forming higher brightness, thus power consumption of the backlights also increases. Therefore, since larger power consumption should be dealt with the low voltage of single power source, some problems such as power efficiency and heat generation are caused.
When a power source of the inverter and the power source of an image board are supplied independently, status information of the inverter is not transmitted to the image board, thus causing a phenomenon that the displayed state is continued even when the backlight power source in the inverter is turned off. Especially, the backlight which consumes more electric power than the image board, is turned off earlier than the image board when the power source is turned on right after the power source is turned off due to an instant electric failure. In addition, when the power source is turned on before the image board is reset (the power source is turned on after the electric failure), the display is made in a state that the power source of the backlight is turned off.